In recent years, the use of smart materials to resolve environmental problems in building applications has been increasingly widespread. In particular, Phase Change Materials (PCMs) are used to improve thermal performance of air conditioning system and building insulation components. PCMs can be used to reduce energy consumption since they are able to store and release heat, stabilizing the thermal profile inside the building. In this work, previously developed composite panels made of PCMs dispersed in a cellulose matrix that derives from waste paper reclaim are studied. In particular, the evaluation of PCM-based composite material in dynamic thermal conditions will be presented and results compared to those obtained with commercial panels without the addition of PCMs. In order to simulate dynamic thermal conditions, a thermostatic chamber has been designed. The panel to be studied constitutes part of the frontal wall; inside the chamber, temperature and radiation profiles are tuned according to real conditions, while the temperature outside the chamber is maintained constant at room temperature. Several parameters are monitored: irradiation intensity, temperature inside the chamber and thermal flux across the panel. Results show the heat storage capacity of PCMs and their effect on improving the thermal insulation of a cellulose-based panel.